The present invention relates to a seat belt retractor for a vehicle or the like, particularly to a seat belt retractor provided with a torsion bar connected to a seat belt.
In the conventional seat belt retractor provided with a torsion bar, a sleeve is integrally connected to one end of the torsion bar and a seat belt is wound round the sleeve. And between the other end of the torsion bar and a fixed member of the retractor such as a holder block, a catch is provided for usually allowing the rotation of the torsion bar and locking the other end of the torsion bar only in an emergency such as upon an impact of the vehicle.
The seat belt is usually withdrawn from or wound up due to the rotation of the sleeve. And in an emergency, the other end of the torsion bar is locked to the fixed member by the catch while one end thereof connected to the sleeve is rotated by the seat belt to which the load of an occupant is applied.
As a result, the torsion bar is twisted to absorb the impact energy of the occupant.
However, in the conventional device as described above, the torsion bar is in danger of being excessively twisted and broken when the vehicle collides against another vehicle or a fixed object at a high speed or the weight of the occupant wearing the seat belt is too large.
If the torsion bar is broken, the occupant is not restricted by the seat belt to be in danger of being injured.
Accordingly, one object of the present invention is to provide an improved and safe seat belt retractor provided with a torsion bar for absorbing the kinetic energy of the occupant in an emergency.
Another object of the present invention is to provide a seat belt retractor provided with a means for preventing the torsion bar from being broken.